https://www.tutorialspoint.com/apache\_pig/apache\_pig\_cogroup\_operator.htm

The COGROUP operator works more or less in the same way as the GROUP operator. The only difference between the two operators is that the group operator is normally used with one relation, while the cogroup operator is used in statements involving two or more relations.

Grouping Two Relations using Cogroup

Assume that we have two files namely student_details.txt and employee_details.txt in the HDFS directory /pig_data/ as shown below.

student_details.txt

001,Rajiv,Reddy,21,9848022337,Hyderabad

002,siddarth,Battacharya,22,9848022338,Kolkata

003,Rajesh,Khanna,22,9848022339,Delhi

004,Preethi,Agarwal,21,9848022330,Pune

005,Trupthi,Mohanthy,23,9848022336,Bhuwaneshwar

006,Archana,Mishra,23,9848022335,Chennai

007,Komal,Nayak,24,9848022334,trivendram

008,Bharathi,Nambiayar,24,9848022333,Chennai

employee_details.txt

001,Robin,22,newyork

002,BOB,23,Kolkata

003,Maya,23,Tokyo

004,Sara,25,London

005,David,23,Bhuwaneshwar

006,Maggy,22,Chennai

And we have loaded these files into Pig with the relation names student_details and employee_details respectively, as shown below.

grunt> student_details = LOAD 'hdfs://localhost:9000/pig_data/student_details.txt' USING PigStorage(',')

as (id:int, firstname:chararray, lastname:chararray, age:int, phone:chararray, city:chararray);

grunt> employee_details = LOAD 'hdfs://localhost:9000/pig_data/employee_details.txt' USING PigStorage(',')

as (id:int, name:chararray, age:int, city:chararray);

Now, let us group the records/tuples of the relations student_details and employee_details with the key age, as shown below.

grunt> cogroup_data = COGROUP student_details by age, employee_details by age;